Built-in AntiSpam Filtering
All of our newer mailservers include built-in NoSpamWeb Anti-Spam features, and we are currently upgrading the older ones to support this functionality as well. Even if your server supports these features, however, they are not automatically enabled for every website since many of our customers would prefer to perform their own spam filtering using 3rd party programs installed on their home computer. If you do wish to enable Anti-Spam filtering on your domain, please contact support@imageaid.net and request to sign up for our NoSpamWeb service.
Here is an brief outline on how our Anti-Spam filtering works on the mailserver.
There are 6 'criteria' for determining whether or not an email is spam:
Blacklists:
- fiveten (blackholes.five-ten-sg.com)
- SpamHaus (sbl.spamhaus.org)
- ybl (ybl.megacity.org)
- Spamcop (bl.spamcop.net)
If the IP address of an e-mail matches one of these black lists, an X-header is inserted into the message header to indicate which black list it matched. Click here for more information on X-headers.
Additional Criteria:
- Verify MAIL FROM Address (also known as FROM Line Verification)
The "From" address of the connecting server is verified for each message to ensure that the user is a valid user on the mail server. If the user or server does not exist, the message is identified as spam. If this test fails, an X-Header is inserted into the message.
- Verify HELO/EHLO Domain
The domain passed during the HELO/EHLO is used to perform a DNS query to verify that the domain specified has an "A" record or an "MX" record. If this test fails, an X-Header is inserted into the message.
Note: The SMTPD service does not accept mail from clients that do not begin the SMTP conversation with "HELO" or "EHLO".
If an email receives a total of 3 or more "X-headers" from the above criteria, it is declared spam and deleted automatically. We are not able to create a white list of email addresses that the spam filter should ignore. If it receives two or less 'X-headers', then it will be delivered normally, however if you wish you can setup a filter within your domain to filter all messages with an X-header for even stricter rules. That filter would look something like this:
If HEADER contains "X-IMAIL-SPAM" |
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